Dentin is the substance between enamel or cementum and the pulp chamber. It is secreted by the odontoblasts of the dental pulp. The formation of dentin is known as dentinogenesis. The porous, yellow-hued material is made up of 70% inorganic materials, 20% organic materials, and 10% water by weight.
Medical Definition of metaplasia. 1  1: transformation of one tissue into another metaplasia of cartilage into bone. 2  2: abnormal replacement of cells of one type by cells of another.
1 Metaplasia-Cells observed under the microscope look normal, but are not the cell type usually found in that bodily tissue or area. 2  Metaplasia is not usually precancerous, but some cases are. 3  Dysplasia-Cells have an abnormal appearance under the microscope and are disorganized.y Sally Robertson, BSc. The term neoplasm refers to an abnormal growth of tissue caused by the rapid division of cells that have undergone some form of mutation. The body is made up of trillions of cells that grow, divide, and die in an orderly fashion.